UPDATE: Just got off phone, I could send in and will be 2-3 weeks. I could take it to a certified glock armorer and it would be less time. The tech claimed that it will likey improve on its own with simply more rounds, allowing the recoils spring to "condition".. get a bit softer. Does this sound like BS or should I just get it fixed?

You will need a pair of pliers to GENTLY remove the 30274 ejector arm from the Gen4 housing that you ordered. Once it is out, put it in your Gen3 housing. Also make sure you install the HRED backwards from the stock plunger configuration.